During the past several years, cladistic analyses of morphological, chemical, and DNA data have made it clear that the recognition of the Saxifragaceaesensu
lato (Engler, Nat. Pflanzenfam. 18a: 74-226. 1928) is untenable. Among the angiosperm families, Saxifragaceae sensu lato may in fact represent the most extreme example of a polyphyleticassemblage
. For example, recent analyses of DNA sequence data indicate that these taxa represent at least ten separate evolutionary lines
, many of which are only distantly related to one another (Morgan & Soltis, Ann. Missouri Bot. Gard. 80: 631-660. 1993; Soltis & Soltis, Amer. J. Bot. 84: 504-522. 1997) . Furthermore, very large molecular phylogenetic
analyses of hundreds
of angiosperms
indicate that these separate lineages
are distributed among four of the six traditionally recognized subclasses of dicotyledons (Savolainen et al.
, Syst. Biol. 49: 306-362. 2000; Soltis et al., Nature 402: 402-404. 1999) . These recent studies have also greatly clarified how this phylogeneticallydiverse
assemblage should be divided
into families and treated taxonomically (see The Angiosperm Phylogeny Group (APG), Ann. Missouri Bot. Gard. 85: 531-553. 1998) . Recent studies of DNA sequence data have clarified both the circumscription and affinities of a narrowly defined Saxifragaceae (Saxifragaceae sensu stricto) and Hydrangeaceae (Soltis et al., Amer. J. Bot. 82: 504-514. 1995; Savolainen et al., loc. cit.
; Soltis et al., loc. cit. 1999) . Saxifragaceae sensu stricto should consist only of Saxifragoideae, a group of about 30 herbaceous genera. Members
of Saxifragaceae sensu stricto from the Chinese flora
include Astilbe, Astilboides, Bergenia, Chrysosplenium, Mitella, Mukdenia, Oresitrophe, Rodgersia, Saxifraga, Tanakaea, Tiarella, and the recently described Saniculiphyllum. Close relatives of Saxifragaceae sensu stricto include Itea, Penthorum, and Ribes. These genera, the sole
members of Iteoideae, Penthoroideae, and Ribesioideae, respectively, are also best treated in separate families: Iteaceae, Penthoraceae, and Grossulariaceae (see APG, loc. cit.) . These taxa, as well as several others, such as Crassulaceae, are basal to a large assemblage of taxa, most of which were traditionally placed in Rosidae
. Sequence data also indicate that Parnassia (the sole member of the Parnassioideae) is a more derived member of the rosid alliance
, most closely related to Brexia and Lepuropetalon (also part of Saxifragaceae sensu lato) and Celastraceae. Parnassia and Lepuropetalon should be placed in Parnassiaceae with Brexia part of an expanded Celastraceae (APG, loc. cit.) .

Both morphological and molecular data indicate that Hydrangeoideae and Escallonioideae are, in contrast, allied with taxa traditionally placed in Asteridae. Hydrangeoideae are a well-defined, monophyletic lineage that should be treated as Hydrangeaceae. In China they include Cardiandra, Decumaria, Deinanthe, Deutzia, Dichroa, Hydrangea, Kirengeshoma, Philadelphus, Pileostegia, Platycrater, and Schizophragma, and are closely allied with families such as Cornaceae, Loasaceae, and Nyssaceae. Escallonioideae appear to be polyphyletic, and this group of approximately 14 genera is in need of thorough study. Members of this subfamily
are allied with several different lineages of higher asterids. Polyosma, the only member of Escallonioideae in China, appears closely allied with Caprifoliaceae (Xiang & Soltis in Boufford & Ohba, Sino-Japanese Flora: its Characteristics and Diversification, 1998) .[1]